16. One Day at a Time (CBS)
The pitch may be simple: Divorcée Ann Romano (the underrated Bonnie Franklin) raises two daughters (Mackenzie Phillips and Valerie Bertinelli) and, essentially, their apartment building's super, Schneider (Pat Harrington). But life was never easy, especially in this fourth season when Ann realizes she's dating a married man and the girls fight over the same boy. Storylines you've heard before, yes? But the best sitcoms make them feel fresh.
Seasons on DVD: The first one